Provider token_type values are not reliably valid HTTP auth schemes
(Slack returns "bot" / "user", some providers send an empty string),
which produces a malformed Authorization header on subsequent
requests. Every OAuth2 connector in this codebase actually uses a
bearer token, so we always send "Bearer".
Signed-off-by: Aurélien Sibiril <81782+aureliensibiril@users.noreply.github.com>
a6379bb9f4